Brown University School of Engineering

Joint Materials/Solid Mechanics Seminar Series “Role of Grain-Boundary Complexions (Equilibrium Interface-Stabilized Phases) in Mechanical Failure”

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Monday, April 30, 2012 4:00pm - 5:00pm

BROWN UNIVERSITY Joint Materials/Solid Mechanics Seminar Series “Role of Grain-Boundary Complexions (Equilibrium Interface-Stabilized Phases) in Mechanical Failure” Martin P. Harmer Department of Materials Science and Engineering and Center for Advanced Materials and Nanotechnology Lehigh University Bethlehem PA 18015 Abstract: A grain boundary complexion is a “phase” that is thermodynamically stabilized by its adjoining grains (Science, 332, 182, 2011). It is chemically and structurally distinct from any bulk phase. Complexion phases can interconvert between well-defined equilibrium structures, which can be represented on complexion phase diagrams analogous to bulk phase diagrams. A progressive series of six possible complexion conformations has been proposed, whereby the discrete number of atomic layers, the layer thickness and the degree of structural and chemical ordering defines the stability of each type of complexion. One well-studied complexion conformation is the equilibrium thickness (1-2nm) intergranular film (IGF). Newly revealed thinner layer complexion conformations include bilayers and trilayers. This talk will discuss the important influence that complexion phases have on the mechanical behavior of materials. The role of a bilayer-phase complexion in liquid metal induced embrittlement of metals will be highlighted. Monday, April 30, 2012 4:00-5:00 pm B&H Room 190